linux-kernel - Re: [mmotm] "x86/atomic: move __arch_atomic_add

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Date:   Thu, 16 Mar 2017 09:41:10 -0700
From:   Andi Kleen <ak@...ux.intel.com>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     20170315021431.13107-3-andi@...stfloor.org,
        Ingo Molnar <mingo@...e.hu>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "x86@...nel.org" <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [mmotm] "x86/atomic: move __arch_atomic_add_unless out of line"
 build error

> Andi, why did you completely remove __arch_atomic_add_unless() from
> the header? Don't we need at least a declaration there?

Actually it's there in my git version:

I wonder where it disappeared.

-/**
- * __atomic_add_unless - add unless the number is already a given value
- * @v: pointer of type atomic_t
- * @a: the amount to add to v...
- * @u: ...unless v is equal to u.
- *
- * Atomically adds @a to @v, so long as @v was not already @u.
- * Returns the old value of @v.
- */
-static __always_inline int __atomic_add_unless(atomic_t *v, int a, int u)
-{
-       int c, old;
-       c = atomic_read(v);
-       for (;;) {
-               if (unlikely(c == (u)))
-                       break;
-               old = atomic_cmpxchg((v), c, c + (a));
-               if (likely(old == c))
-                       break;
-               c = old;
-       }
-       return c;
-}
+int __atomic_add_unless(atomic_t *v, int a, int u);